Asthma morbidity is high among inner city children. The factors responsible for this public health problem remain unclear but are probably related to genetics, psychosocial factors, and exposures to allergens and air pollutants, including environmental tobacco smoke, particles, ozone and nitrogen dioxide. The proposed epidemiologic project aims to elucidate the relationship between exposures to allergens and air pollutants and asthma morbidity among inner city children with asthma. The specific aims are: (1) to characterize exposure to allergens and air pollutants among inner city children with asthma; (2) to determine the prevalence of respiratory morbidity among inner city children with asthma; and (3) to assess whether exposure to higher levels of both air pollutants and allergens results in more asthma morbidity than expected based on the effects from independent exposures to air pollutants and allergen. This community-based epidemiologic project will enroll children who currently have symptomatic asthma in an asthma education program in 25 elementary schools and invite them participate in a study of the relationship of asthma to air pollution. Participants (expected n= 300) will be recruited over a 3 year period. Children and their families will undergo a clinic visit with interviews on demographics, psychosocial, past and current asthma health status, exposure to passive smoking, and time-activity patterns. Children will receive allergy skin tests, and provide spirogram, urine for cotinine and serum for total IgE. Children's homes will be visited to ascertain the physical condition, and measure allergens in settled dust, airborne PM/2.5 and PM/10, ozone, NO2 and cotinine. Data on ambient measurements of pollutants will be obtained from the State of Maryland (ozone and NO2 and a USA EPA monitoring station (particles) in the study community. A sample of study children (n=200) will be interviewed six months after baseline to assess asthma status. Analysis will examine whether asthma morbidity is associated with exposure to allergens, pollutants or a combination, and whether apparent seasonal variations in asthma morbidity are associated with seasonal variations in allergens and pollutants. The goal of this effort is to identify environmental factors associated with asthma morbidity that may help in the development of cost-effective community-based interventions in urban environments.